Its a must watch. Do not spoil the movie by watching or reading reviews. Just go to the theatre near you and have great fun.
Just believe in whatever the director wants to convey and you'll enjoy.
For those who still want a review:
Best Part: Suspence, awesome VFX, great screenplay, charismatic Rajnikant, a really great villain, short and sweet movie, no distractions as there are no songs, a good message at the end.
Worst Part: It ended soon. I wanted to see more..
There might be places where you won't like the explanations to things which you do not understand but who cares when you can enjoy it without thinking too much.